Post holiday binary trading
Using Wireshark I captured the tcp packages being sent and received while requesting the image and displaying it right as well as requesting the image and having it fail to render. Also, the format of the gif what kind of encoding?''. It has been verified to be consistent on different networks, computers and Firefox versions, the format is GIF87a (previously I said 67, sorry, that doesn't even exists). Sadly, I am currently not able to reproduce the behavior in a different system or using a different resource.
In this case flushing the dnscache may be helpful, but I do not know what OS you are running.